Radio frequency guide wire assembly with optical coherence reflectometry guidance

ABSTRACT

A guide wire assembly includes a guide wire, an optical fiber, and an insulating coating. The guide wire has a distal end, a proximal end, and a bore extending through the wire between the distal and proximal ends. The an optical fiber also includes a distal end and a proximal end and is located within the bore of the guide wire. The optical fiber extends at least between the distal and proximal ends of the guide wire. The insulating coating is around an outside diameter of the guide wire, and is applied such that the distal ends of the guide wire and optical fiber are exposed.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to medical guide wires andcatheters and more particularly, to guiding assemblies and guidingmethods for guide wires.

[0002] Disease processes, e.g., tumors, inflammation of lymph nodes, andplaque build-up in arteries, often afflict the human body. As onespecific example, atherosclerotic plaque is known to build up in thewalls of arteries in the human body. Such plaque build-up restrictscirculation and often causes cardiovascular problems, especially whenthe build-up occurs in coronary arteries.

[0003] To treat such disease, it often is necessary to guide a medicaldevice to the diseased site, and then use the medical device to treatthe diseased area. Commonly a guide wire is used to help guide othertreatment devices. A guide wire typically is required to properlyposition a catheter in an artery. The guide wire is advanced and forms apath, through the artery and region of plaque build-up. The catheter orother device such as a balloon or rotational atherectomy device is thenguided through the artery using the guide wire as a rail.

[0004] Known guide wires exist for the treatment of tissue. For example,known guide wires use laser energy to remove plaque build-up on arterywalls as the guide wire is advanced. One known catheter includes a lasersource and a guide wire body. The guide wire body has a first end, asecond end, or head, and several optic fibers extending between thefirst end and the second end. The laser source is coupled to each of theoptic fibers adjacent the catheter body first end and is configured totransmit laser energy simultaneously through the optic fibers.

[0005] To remove arterial plaque, for example, the guide wire body ispositioned in the artery so that the second end of the guide wire bodyis adjacent a region of plaque build-up. The laser source is thenenergized so that laser energy travels through each of the optic fibersand substantially photoablates the plaque adjacent the second end of thecatheter body. The guide wire body is then advanced through the regionto photoablate the plaque in the entire region.

[0006] However, it often is difficult to guide known guide wires throughthe body without risking damage. For example, known guide wirestypically cannot be easily advanced through partially or totallyoccluded arteries without substantial risk of damaging or puncturing theartery wall. As the guide wire is advanced through the artery, it willencounter obstructions to advancement including plaque build-up or theartery wall itself. However, known guide wires typically do notdistinguish between plaque build-up and the artery wall. An operator maytherefore incorrectly identify an obstruction as plaque build-up andattempt to push the guide wire through the obstruction, resulting ininjury or puncture of the artery wall.

[0007] Even if the direction of the artery is known, often it is notpossible to pass a guide wire through the occlusion because the lesionis too resistant or it is a refractory lesion. In this case, it would bedesirable to have a means to ablate the diseased tissue, but not damagethe healthy tissue. Laser energy is known as a means of photoablation ofthe tissue, healthy or diseased. Likewise, radio frequency energy isknown as a means of thermal ablation of the tissue, healthy or diseased.

BRIEF DESCRIPTION OF THE INVENTION

[0008] In one embodiment, a guide wire assembly is provided whichcomprises a guide wire further comprising a distal end, a proximal end,and a bore extending therethrough between the distal end and theproximal end. The guide wire assembly also comprises an optical fiberhaving a distal end and a proximal end and located within the bore ofthe guide wire. The optical fiber extends from the distal end of theguide wire to the proximal end of the guide wire. An insulating coatingextends around an outside diameter of the guide wire and is applied suchthat the distal end of the guide wire and the distal end of the opticalfiber are exposed.

[0009] In another embodiment, a bi-polar guide wire assembly is providedwhich comprises an inner guide wire further comprising a distal end, aproximal end, and a bore extending therethrough between the distal endand the proximal end. The assembly further comprises an optical fibercomprising a distal end and a proximal end and located within the boreof the inner guide wire. The optical fiber extends at least from thedistal end of the inner guide wire to the proximal end of the innerguide wire. The assembly further comprises an insulating layersurrounding the inner guide wire. The insulating layer comprises adistal end and a proximal end. The guide wire assembly also comprises anouter guide wire having a distal end, a proximal end, and a boreextending therethrough between the distal end and the proximal end. Theinner guide wire, optical fiber, and insulating layer are positionedwithin the bore of the outer guide wire.

[0010] In still another embodiment, an RF ablation apparatus is providedwhich comprises a guide wire assembly, an optical coherencereflectometer connected to the proximal end of the optical fiber, and anRF power source connected between the guide wire and a RF power returnpath.

[0011] In a further embodiment, a method for controlling an ablationprocess, using a radio frequency (RF) ablation system is provided. Thesystem includes a radio frequency power section, an optical coherencereflectometer, a guide wire assembly optically connected to thereflectometer and electrically connected to the RF power source, theelectrical connection being controlled through a control switch. Themethod comprises extending a distal end of the guide wire assemblythrough diseased artery segments to lesions by percutaneous introductionthrough a body extremity, using OCR guidance to position the distal endagainst a lesion, applying RF power at the distal end of the guide wireassembly to ablate the lesion, and removing RF power upon an OCRdetection of healthy tissue near the distal end of the guide wireassembly.

[0012] In another embodiment, a method for performing a transmyocardialrevascularization procedure using a radio frequency (RF) ablation systemis provided. The system includes a radio frequency power section, anoptical coherence reflectometer (OCR), a guide wire assembly opticallyconnected to the reflectometer and electrically connected to the RFpower source, the electrical connection being controlled through acontrol switch. The method comprises extending a distal end of the guidewire assembly to an inner wall surface of a left ventricle of a heart,applying RF power to the distal end, ablating a hole within the innerwall surface, and using a signal from the OCR to stop ablation at aselected distance from an interface between the myocardium andepicardium.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a guide wire assembly.

[0014]FIG. 2 is a sectional view of the guide wire assembly of FIG. 1.

[0015]FIG. 3 is a sectional view of a bipolar guide wire assembly.

[0016]FIG. 4 is a schematic illustration of a radio frequency ablationsystem.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIG. 1 illustrates one embodiment of a guide wire assembly 20. Inone application, guide wire assembly 20 utilizes optical coherencereflectometry (OCR) to control an RF ablation feature implemented usingguide wire assembly 20. Referring specifically to guide wire assembly20, there is included a metal guide wire 24 having a cylindrical bore 26therethrough. An optical fiber 28 is located within bore 26 of guidewire 24. Guide wire assembly 20 is configured to be inserted into a bodypassage (not shown) such as a blood vessel. Guide wire assembly 20further includes an insulation coating 30 extending over guide wire 24as further described below. Guide wire 24 has a distal end 32 and aproximal end 34 and optical fiber 28 also includes a distal end 36 and aproximal end 38. As referred to herein, “distal end” refers to an endfirst inserted into the body passage and “proximal” refers to an endopposite the “distal end”. Distal ends 32 and 36 are positioned within ablood vessel (not shown) adjacent tissue through which a guide wire isto be advanced, e.g., plaque (not shown). Guide wire 24 may be formed,for example, with a coiled wire, as well known in the art.

[0018] Proximal end 34 of guide wire 24 is, in one embodiment,configured with an electrical connector 40, to allow electricalconnection of guide wire 24 to an electrical lead 42. Lead 42 isattached to guide wire 24 by at least one of soldering, crimping, andwelding to proximal end 34. Lead 42 is terminated with any standardelectrical connector for interfacing with RF generation equipment (shownin FIG. 4) used to ablate tissue at distal end 32 of guide wire 24.Similarly, proximal end 38 of optical fiber 28 is configured to beconnected to optical equipment 44, for example an optical coherencereflectometer (OCR) (shown in FIG. 4). Integration of optical fiber 28into guide wire assembly 20, along with OCR, provides a controlmechanism for the ablation process by providing reflections of the areain front of guide wire 24. Reflections are used to determine if it issafe to ablate objects, for example, tissue and plaque, within a region.In addition, reflections are used to determine if it is unsafe to ablateobjects, for example, healthy tissue (i.e. guide wire 24 is adjacenthealthy tissue). In one embodiment, distal end 38 is connected directlyto optical equipment 44. In alternative embodiments, distal end 38 isconnected to optical equipment 44 through a series of opticalinterconnections, as is well known in the art.

[0019]FIG. 2 is a sectional view of distal end 52 of guide wire assembly20. Distal end 32 of guide wire 24 and distal end 36 of optical fiber 28are exposed since insulating coating 30 has been removed at distal end52 of guide wire assembly 20. In one embodiment, about 0.25 to about0.001 inch of distal end 32 of metal guide wire 24 is exposed. Inanother embodiment, about 0.1 to about 0.01 inch of distal end 32 ofmetal guide wire 24 is exposed. In yet another embodiment, about 0.01inch of distal end 32 of metal guide wire 24 is exposed. In stillanother embodiment, about 0.1 inch of distal end 32 of metal guide wire24 is exposed. In an embodiment not shown insulating coating 30 isconfigured, either through application or removal after application,such that only a cross section of distal end 32 of metal guide wire 24and distal end 36 of optical fiber 28 are exposed. In alternativeembodiments, insulating coating 30 is one or more ofpolytetrafluoroethylene (PTFE) material, polyimide, or a conformalcoating such as polyparaxylylene (Parylene).

[0020] In one embodiment, guide wire assembly 20 is a monopolar RF guidewire assembly and is used in conjunction with a grounding plate (shownin FIG. 4). The grounding plate contacts a patient and provides a returnpath for RF power transmitted at distal end 32 of metal guide wire 24during an ablation process.

[0021]FIG. 3 is a sectional view of a distal end 102 of a bi-polar guidewire assembly 104. Assembly 104 includes an inner guide wire 106 havinga bore 108 therethrough from a distal end 110 to a proximal end (notshown). An optical fiber 112 is within bore 108 of inner guide wire 106and extends at least from distal end 110 to the proximal end (not shown)of assembly 104. Inner guide wire 106 is insulated about itscircumference and along its length with an insulating layer 114. Inalternative embodiments, insulating coating 114 is one or more ofpolytetrafluoroethylene (PTFE) material, polyimide, epoxy, nylon, rubberor a conformal coating such as polyparaxylylene (Parylene). Insulatinglayer 114 of a length which prevents electrical contact from occurringbetween inner guide wire 106 and an outer guide wire 116. Outer guidewire 116 includes a bore 118 therethrough from a distal end 120 to aproximal end (not shown). In the embodiment shown, optical fiber 112,inner guide wire 106, and insulating layer 114 are located within bore118 of outer guide wire 116. Guide wire assembly 104 further includes aninsulating coating 122, similar in composition and application toinsulating coating 30 (shown in FIG. 2), which insulates at least aportion of an outside diameter 124 of outer guide wire 116.

[0022] Distal end 110 of inner guide wire 106, distal end 120 of outerguide wire 116, and distal end 126 of optical fiber 112 are exposed asinsulating coating 122 has been removed at distal end 102 of guide wireassembly 104. To expose distal end 110 of inner guide wire 106 a portionof insulating layer 114 is also removed. In one embodiment, from about0.001 inch to about 0.25 inch of distal ends, 110 and 120 of guide wires106 and 116, respectively, are exposed. In another embodiment, fromabout 0.01 inch to about 0.1 inch of distal ends 110 and 120 of guidewires 106 and 116, respectively, are exposed. In still anotherembodiment, not shown, insulating coating 122 is applied such that onlya cross section of distal ends 110, 120 of guide wires 106, 116, an endof insulating layer 114, and distal end 126 of optical fiber 112 areexposed. In alternative embodiments, insulating coating 122 is one ormore of polytetrafluoroethylene (PTFE) material, polyimide, or aconformal coating such as polyparaxylylene (Parylene).

[0023] Guide wire assembly 104 is a bi-polar RF guide wire assembly. Inone embodiment, inner guide wire 106 provides a return path for RF powertransmitted at distal end 120 of outer guide wire 116 during an ablationprocess. In an alternative embodiment, polarity of guide wire assembly104 may be reversed, with outer guide wire 116 providing a return pathfor RF power and inner guide wire 106 transmitting the RF power. In suchan embodiment, insulating coating 122 is optional. In specificembodiments, bi-polar guide wire assembly 104 has a diameter of at least0.010 inches.

[0024] Optical fibers 36 (shown in FIGS. 1 and 2) and 112 are configuredto emit energy waves substantially co-axially with respect to the distalends of guide wire assemblies 20 (shown in FIG. 1) and 104. In oneembodiment, an illumination source is a low coherent illuminationsource, for example, a light emitting diode as known in the art. Opticalfibers 28 (shown in FIG. 1) and 112 are fabricated from drawn orextruded glass or plastic having a central core and a cladding of alower refractive index material to promote internal reflection. In oneembodiment, optical fibers 28 and 112 are polarization-preserving singlemode optic fibers which preserve the plane of polarization of a lightbeam as it propagates along the length of a fiber.Polarization-preserving optic fibers maintain the polarization of thelight beam by having asymmetry in the fiber structure, either in theoverall shape of the fiber, or in the configuration of the cladding withrespect to the central core. In one embodiment, the diameter of each offibers 28 and 112 is about 125 microns, but the diameter may vary.

[0025]FIG. 4 is a radio frequency (RF) ablation system 150 whichincorporates optical coherence reflectometry. System 150 includes an RFpower section 152, which includes an electrosurgical power generator154, a waveform modulator 156 and a frequency power modulator 158.System 150 further includes an optical coherence reflectometer 160 whoseoperation is controlled through computer 162 which has a display 164.Reflectometer 160 is optically connected to optical fiber 166, whichextends to proximal ends of fibers 28 and 112 (shown in FIGS. 2 and 3respectively), which form a portion of guide wire 168. Guide wire 168,is in alternative embodiments, one of guide wire assemblies 20 and 104(described in FIGS. 1 and 3). A ground plate 170 provides a return pathfor RF power when an embodiment of system 150 incorporates guide wireassembly 20.

[0026] Electrosurgical power generator 154 provides RF power andtypically operates with a frequency range of about 200 kHz to about 35MHz. In the ablation process, a more typical frequency range is about500 kHz to about 2 MHz. Open circuit voltages range from about 100V toabout 10 kV. Output of generator 154 is waveform modulated so thatdesired ablation effects are obtained. Coagulation is achieved by usingdampened sinusoidal pulses to modulate the RF power at lowerfrequencies. In one embodiment, the RF output is in a range of about 200kHz to about 2 MHz and pulsed (modulated) by wave form modulator 156 ata rate of about 100 Hz to about 10 kHz. Cutting (ablation) is achievedthrough higher RF power output at higher frequencies. In one embodiment,frequencies used for ablation range from about 500 kHz to about 2.5 MHzand an open circuit voltage as high as 1 kV. Although sinusoidal wavesare one embodiment of waveform modulation, other waveform modulationpatterns are used in alternative embodiments.

[0027] In one embodiment, optical fiber 166 connects Optical CoherenceReflectometer (OCR) 160 to guide wire 168 to allow visualization of thetissue in front of guide wire 168. Low coherence near infrared lightfrom a light emitting diode (not shown) is input into the optical fibersystem. In OCR 160, the low coherence light is divided into two beamswith one beam being diverted to optical fiber 166 and thus to guide wire168. The second (reference) beam stays within OCR 160 in a fiber thathas a path length equivalent to a path length of the fiber from the OCR160, through fiber 166 and guide wire 168. In one embodiment, OCR 160 isconfigured in a Michelson interferometer configuration. The optical pathlength in the second (reference) beam is varied, either mechanically bymoving a mirror at the end of the fiber within OCR 160 or by stretchingthe fiber, for example, as is done with PZT stretchers. The effect isthat the light scattered by the tissue back into guide wire 168recombines with the light from the second beam such that an interferencepattern is generated for light that is scattered from the tissue at anequivalent path length as the second beam. By knowingly varying the pathlength of the second (reference) beam, an interference intensity versusdistance profile can be generated.

[0028] It has been shown that a light scattering intensity increasesfrom the normal arterial wall compared to the scattering properties ofthe occlusive materials. This same characteristic can be shown for otherinterfaces such as the boundary of tumor and healthy tissue. Analgorithm configures computer 162 to analyze the scattering intensityversus distance data to determine if there is a sharp increase in therelative scattering within the interferometer sweep. If a sharp increaseis detected, the operator is warned that the arterial wall is close anda control signal which enables RF energy output from generator 154changes state, stopping RF output from generator 154 and thereforestopping delivery of RF energy to guide wire 168.

[0029] In an alternative embodiment, output of generator 154 isfrequency power modulated to deliver bursts of RF power followed bydeadtime, thereby allowing any heat present near the ablation area todissipate. Utilization of deadtime prevents heat buildup that coulddamage adjacent tissue.

[0030] In different embodiments, RF power output of generator 154 isgated by different logical controls. A control switch 172 provides thegating for the different controls. A first gating mechanism is an OCRsignal received over optical fiber 166 at OCR 160. The OCR signal is afeedback signal which is monitored through utilization of computer 162.Computer 162 also provides a gating signal to control switch 172,controlling RF output over an electrical contact 174 to assure that adistal tip 176 of guide wire 168 contacts tissue to be ablated. The OCRsignal is further monitored to assure that an interface betweenunhealthy and healthy tissue is not near distal tip 176 thus assuringthat the ablation will only affect unhealthy (targeted) tissue. In thecase of a total occlusion, the OCR signal is monitored to assure thatthe normal artery wall (media) is not near, whereas in a percutaneoustransmyocardial revascularization (PTMR) procedure the OCR signal ismonitored for an epicardium interface while myocardial tissue is beingablated. The OCR signal, which is monitored utilizing an algorithmrunning in computer 162, yields a go/no-go signal for gating the RFpower.

[0031] In a second embodiment, RF power output transferred to distal tip176 through electrical contact 174 is controlled using an operatorswitch 178. In one embodiment, operator switch 178 is a foot switch orany switch accessible by an operator. In another embodiment, control ofthe RF power applied for ablation by an operator is contemplated. Insuch an embodiment, switch 178 is integrated into a catheter handle (notshown) which is utilized for advancement of guide wire 168. In such anembodiment, when the operator advances guide wire 168, switch 178 closesallowing the RF power to ablate with the advancement.

[0032] In still another embodiment, control switch 172 is gated byincorporation of an EKG monitor 180 to assure that RF power is notapplied during the S-T segment period. The heart is most sensitive toelectrical stimulation during this time and by blocking RF output duringthis period, a patient is protected from arrhythmias.

[0033] It is to be appreciated that any combination of the abovedescribed gating mechanisms can be used, and which gating mechanisms areused in any one application depends on the particular application andrisk to the patient. In the above described embodiments, computer 162 isconfigured to generate data from the ablation process and display thedata on display 164, thereby providing an operator feedback regarding anablation process.

[0034] RF ablation system 150 with incorporation of OCR guidance hasmany applications in medical practice. System 150 can be used wherever aconventional guide wire is used, but offers the additional features oftissue ablation and guidance. It will be appreciated that the examplesdescribed below are not limiting, but rather, the examples are forpurposes of illustration. For example, atherosclerotic disease severelyimpairs the arterial functions with the formation of plaques, atheromas,and thrombus in the vessel. This disease is routinely treated byinterventional angioplasty. In such a treatment, traditional guide wiresare threaded through the diseased artery segments by percutaneousintroduction through a body extremity. Angioplasty balloons or otheratherectomy devices are used to dilate and re-establish flow within theartery.

[0035] However, when treated using the OCR guided RF ablation of system150, guide wire 168 is used to cross highly resistant lesions. OCRguidance assures the operator that guide wire 168 is within the lumenand RF ablation provides a hole within the lesions for the wire to passthrough. The operator identifies diseased artery segments underangiographic examination with x-ray imaging and the introduction ofcontrast into the blood field. Commercially available introducers andguide catheters are then used to establish access to the diseasedregion. The OCR/RF guide wire 168 of system 150 is guided to thetargeted segment under x-ray imaging and placed adjacent the diseasedblockage. The operator then attempts to push guide wire 168 into thelesion using the OCR signal to assure that the wire is within the lumenand not too close to the normal artery wall. If the lesion is tooresistant, wire 168 will buckle or the supporting catheter will beforced back (proximal), rather than guide wire 168 advancing. In such acase, the operator selects the RF ablation mode. The OCR processing incomputer 162 assures that distal tip 176 of guide wire 168 is againsttissue and that the artery wall is not too close. If necessary, thepatient's EKG is monitored with monitor 180 to trigger the RF powerduring a non-critical time of the coronary cycle. Distal tip 176, whenenergized, will create a small spark ablating the tissue in front of thewire. The energy is pulsed, as described above, to allow generated heatto dissipate, preventing collateral tissue damage from excessive heatstorage. The process is repeated to create a hole through the lesionthrough which wire 168 can pass. If the OCR signal detects a normalartery wall, RF power is removed to prevent damage to the artery.

[0036] Transmyocardial revascularization (TMR) is a recent therapy forpatients that have severe angina and other treatment modalities havefailed. Small channels are ablated into the myocardium to revascularizethe ischemic tissue. The OCR/RF guide wire system 150 is used to createthe channels or holes within the myorcardial tissue. Catheters are usedto gain percutaneous access to the left ventricle of the heart. Guidewire 168 is introduced through the catheter and positioned adjacent tothe inner wall surface. Wire 168 is positioned by x-ray imaging, andadvanced into the tissue while energized, ablating a hole. The OCRsignal is used to control the depth of the hole. Ablation is stoppedwhen the interface between the myocardium and epicardium is approached,preventing perforation of the heart. The OCR signal is also used toprevent perforation of a coronary artery.

[0037] OCR/RF guide wire system 150 provides a safe method foradvancement of guide wire 168 into a vessel. Guide wire 168 further is amechanism which provides information to help an operator distinguishamong the types of obstructions which might be obstructing advancementof the guide wire. However, it is to be understood that the abovedescribed guide wire and methods for implementing treatments whichimplement system 150 are exemplary and other embodiments are possible.For example, in another embodiment, guide wire 168 may be made with aharder and less flexible distal end (for example, made of hardenedsteel) to make it more suitable to go through a partially occludedartery. The guide wire may also be coated with a friction reducingmaterial such as, for example, a polymer or a hydrophilic coating asknown in the art. The coating reduces the surface friction to easeadvancing the guide wire further into the vessel. The guide wire mayalso include a thin metal wire positioned next to the fiber optic whichcan be pulled back making the guide wire end very floppy. The metalwire, when extended, stiffens the distal end portion of the guide wire.

[0038] While the invention has been described in terms of variousspecific embodiments, those skilled in the art will recognize that theinvention can be practiced with modification within the spirit and scopeof the claims.

What is claimed is:
 1. A guide wire assembly comprising: a guide wirecomprising a distal end, a proximal end, and a bore extendingtherethrough between said distal end and said proximal end; an opticalfiber having a distal end and a proximal end and located within saidbore of said guide wire, said optical fiber extends from said distal endof said guide wire to said proximal end of said guide wire; and aninsulating coating extending around an outside diameter of said guidewire, said insulating coating configured such that said distal end ofsaid guide wire and said distal end of said optical fiber are exposed.2. A guide wire assembly according to claim 1 wherein said insulatingcoating is configured such that about 0.001 inch to about 0.25 inch ofsaid distal end of said guide wire is exposed.
 3. A guide wire assemblyaccording to claim 1 wherein said insulating coating is applied suchthat about 0.01 inch to about 0.1 inch of said distal end of said guidewire is exposed.
 4. A guide wire assembly according to claim 1 whereinsaid insulating coating comprises a polytetraflouroethylene material, apolyimide material, and a polyparaxylylene conformal coating.
 5. A guidewire assembly according to claim 1 wherein said proximal end of saidguide wire is configured for electrical contact with a conductor.
 6. Aguide wire assembly according to claim 5 wherein electrical contact witha conductor is attained through at least one of soldering, crimping, andwelding.
 7. A bi-polar guide wire assembly comprising: an inner guidewire comprising a distal end, a proximal end, and a bore extendingtherethrough between said distal end and said proximal end; an opticalfiber comprising a distal end and a proximal end and located within saidbore of said inner guide wire, said optical fiber extending at leastfrom said distal end of said inner guide wire to said proximal end ofsaid inner guide wire; an insulating layer comprising a distal end and aproximal end, said insulating layer surrounding said inner guide wire;and an outer guide wire having a distal end, a proximal end, and a boreextending therethrough between said distal end and said proximal end,said inner guide wire, said optical fiber, and said insulating layerpositioned within said bore of said outer guide wire.
 8. A guide wireassembly according to claim 7 further comprising an insulating coatingaround an outside diameter of said outer guide wire, said insulatingcoating configured such that at least said distal end of said innerguide wire, said distal end of said outer guide wire, said distal end ofsaid insulating layer, and said distal end of said optical fiber areexposed.
 9. A guide wire assembly according to claim 8 wherein saidinsulating coating and said insulating layer are configured such thatabout 0.001 inch to about 0.25 inch of said distal ends of said innerguide wire and said outer guide wire are exposed.
 10. A guide wireassembly according to claim 8 wherein said insulating coating and saidinsulating layer are configured such that about 0.01 inch to about 0.1inch of said distal ends of said inner guide wire and said outer guidewire are exposed.
 11. A guide wire assembly according to claim 8 whereinsaid insulating coating comprises a polytetraflouroethylene material, apolyimide material, and a polyparaxylylene conformal coating.
 12. Aguide wire assembly according to claim 7 wherein said proximal ends ofsaid inner guide wire and said outer guide wire are each configured forelectrical contact with separate conductors.
 13. A guide wire assemblyaccording to claim 12 wherein electrical contact with separateconductors comprises at least one of soldering, crimping, and weldingseparate conductors to said inner guide wire and said outer guide wire.14. A guide wire assembly according to claim 7 wherein said assembly hasa diameter of at least 0.010 inch.
 15. A guide wire assembly accordingto claim 7 wherein said insulating layer comprises apolytetraflouroethylene material, a polyimide material, an epoxy, nylon,rubber, and a polyparaxylylene conformal coating.
 16. A radio frequency(RF) ablation apparatus comprising: a guide wire assembly; an opticalcoherence reflectometer optically connected to an proximal end of saidguide wire assembly; and an RF power source electrically connectedbetween said guide wire assembly and a return path for RF power.
 17. AnRF ablation apparatus according to claim 16 wherein said RF power sourcecomprises: an electrosurgical RF power generator; a wave form modulator;and a frequency power modulator.
 18. An RF ablation apparatus accordingto claim 17 wherein said electrosurgical power generator has a frequencyrange of about 200 kHz to about 35 MHz.
 19. An RF ablation apparatusaccording to claim 17 wherein said wave form modulator is configured tomodulate said electrosurgical RF power generator from about 100 Hz toabout 10 kHz.
 20. An RF ablation apparatus according to claim 16 whereinsaid guide wire assembly comprises: a guide wire comprising a distalend, a proximal end, and a bore extending therethrough between saiddistal end and said proximal end; an optical fiber comprising a distalend and a proximal end and located within said bore of said guide wire,said optical fiber extending at least from said distal end of said guidewire to said proximal end of said guide wire; and an insulating coatingaround an outside diameter of said guide wire, said insulating coatingconfigured such that said distal end of said guide wire and said distalend of said optical fiber are exposed.
 21. An RF ablation apparatusaccording to claim 20 wherein the RF return path comprises a groundingplate.
 22. An RF ablation apparatus according to claim 16 wherein saidguide wire assembly comprises: an inner guide wire comprising a distalend, a proximal end, and a bore extending therethrough between saiddistal end and said proximal end; an optical fiber comprising a distalend and a proximal end and located within said bore of said inner guidewire, said optical fiber extending at least from said distal end of saidinner guide wire to said proximal end of said inner guide wire; aninsulating layer comprising a distal end and a proximal end, saidinsulating layer surrounding said inner guide wire; and an outer guidewire comprising a distal end, a proximal end, and a bore extendingtherethrough between said distal end and said proximal end, said innerguide wire, said optical fiber, and said insulating layer positionedwithin said bore of said outer guide wire.
 23. An RF ablation apparatusaccording to claim 22 wherein said guide wire assembly comprises aninsulating coating around an outside diameter of said outer guide wire,said insulating coating configured such that at least said distal end ofsaid inner guide wire, said distal end of said outer guide wire, saiddistal end of said insulating layer, and said distal end of said opticalfiber are exposed, one of said inner guide wire and said outer guidewire providing the return path for RF power.
 24. An RF ablationapparatus according to claim 16 further comprising an EKG monitor, saidmonitor configured to gate RF power from said RF power source to ensureRF power is not applied during an S-T segment period.
 25. An RF ablationapparatus according to claim 16 further comprising an operator switch,said switch configured to gate RF power from said RF power source uponclosure of the switch by an operator.
 26. An RF ablation apparatusaccording to claim 16 further comprising a computer coupled to saidoptical coherence reflectometer (OCR), said computer configured to gateRF power from said RF power source based upon an OCR feedback signal.27. An RF ablation apparatus according to claim 26 wherein said computeris configured with an algorithm to analyze a scattering intensityagainst distance data received from said OCR to determine any increasesin relative scattering.
 28. An RF ablation apparatus according to claim27 wherein if an increase in relative scattering is detected, saidcomputer is configured to warn an operator that an arterial wall isclose to said distal end of said guide wire and cause RF power to beremoved from said guide wire assembly.
 29. An RF ablation apparatusaccording to claim 26 wherein the OCR feedback signal is monitored toensure that a distal tip of said guide wire assembly is in contact withtissue to be ablated.
 30. An RF ablation apparatus according to claim 26wherein the OCR feedback signal is monitored to ensure that an interfacebetween healthy and unhealthy tissue is not near a distal tip of saidguide wire assembly.
 31. An RF ablation apparatus according to claim 26wherein the OCR feedback signal is monitored to ensure that an arterywall is not near a distal tip of said guide wire assembly.
 32. An RFablation apparatus according to claim 26 wherein during a percutaneoustransmyocardial revascularization procedure, the OCR feedback signal isused to monitor for an epicardium interface while myocardial tissue isbeing ablated.
 33. A method for controlling an ablation process, using aradio frequency (RF) ablation system, the system including a radiofrequency power section, an optical coherence reflectometer, a guidewire assembly optically connected to the reflectometer and electricallyconnected to the RF power source, the electrical connection beingcontrolled through a control switch, said method comprising: threading adistal tip of the guide wire assembly through diseased artery segmentsto lesions by percutaneous induction through a body extremity; using OCRimaging to assure an operator that the distal tip is against a lesion;ablating the lesion by applying RF power at the distal tip of the guidewire assembly; and removing RF power upon an OCR detection of healthytissue near the distal tip of the guide wire assembly.
 34. A methodaccording to claim 33 wherein ablating the lesion by applying RF powercomprises modulating the RF power thereby allowing heat to dissipate.35. A method for performing a transmyocardial revascularizationprocedure using a radio frequency (RF) ablation system, the systemincluding a radio frequency power section, an optical coherencereflectometer (OCR), a guide wire assembly optically connected to thereflectometer and electrically connected to the RF power source, theelectrical connection being controlled through a control switch, saidmethod comprising: threading a distal tip of the guide wire assembly toan inner wall surface of a left ventricle of a heart; applying RF powerto the distal tip; ablating a hole within the inner wall surface; andusing a signal from the OCR to stop ablation when an interface between amyocardium and epicardium is approached.
 36. A method according to claim35 wherein using a signal from the OCR to stop ablation comprises usingthe signal from the OCR to control the control switch thereby openingthe electrical connection to the RF power source.